The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to integrate filters onto monolithic semiconductor devices. Typically such filters were limited to simple pi-type filters that included resistive and capacitive elements or in some cases inductive and passive elements. One example of a pi-type filter was the NUF6106 sold by ON Semiconductor of 5005 East McDowell Road, Phoenix Ariz. The pi-type filters often did not provide sufficient attenuation above the cut-off frequency of the filter. The filters that included inductors typically were pi-type filters with a series inductor coupled in series with the pi-type filter. One example of such a filter is disclosed in U.S. patent application publication number U.S. 2003/0228848. Inductive filters typically had excessive loss at frequencies above the cut-off frequency of the filter (typically referred to as insertion loss), and often had undesirable group delay distortion.
Accordingly, it is desirable to have a filter integrated onto a monolithic semiconductor device that as low group delay distortion, low insertion loss below the cut-off frequency, and high loss above the cut-off frequency.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. For clarity of the drawings, doped regions of device structures are illustrated as having generally straight line edges and precise angular corners. However, those skilled in the art understand that due to the diffusion and activation of dopants the edges of doped regions are generally not straight lines and the corners are not precise angles.